Field of the Invention
This invention relates generally to the field of geophysical exploration for hydrocarbons. More specifically, the invention relates to a method of faster and more efficient grid processing in seismic modeling.
Background of the Invention
Scientists and engineers often employ geophysical surveys for exploration and engineering projects. Geophysical surveys can provide information about underground structures, including formation boundaries, rock types, and the presence or absence of fluid reservoirs. Such information greatly aids searches for water, geothermal reservoirs, and mineral deposits such as hydrocarbons and ores. Oil companies in particular often invest in extensive seismic and electromagnetic surveys to select sites for exploratory oil wells.
Geophysical surveys can be performed on land or in water. As indicated in the example survey of FIG. 1, an energy source 102 near the region of interest 104 generates waves 106 that propagate into the region of interest and reflect from internal features such as bed boundaries. Some of the reflected wave 108 energy eventually reaches an array of receivers 110 on the surface 112. A recording system 114 captures the received signals for storage and processing. The process is repeated with many different source positions and optionally with different receiver positions. Although various methods exist for converting the received wave signals into an image of the subsurface structure, the most popular such techniques employ finite difference wave field modeling, a process that propagates waves forward or backward in time using discrete time steps and fast approximations of wave function derivatives. With small enough time steps and accurate enough approximations, the finite difference wave field modeling process provides an efficient, high fidelity solution. Nevertheless, the finite difference modeling process imposes a substantial computational demand.
Many efforts have been made to satisfy the computational demands of the finite difference wave field modeling process. Many combined hardware-software solutions have been implemented in the attempt to maximize runtime efficiency. In addition to exploiting different parallelization strategies offered by different hardware systems, the software is often customized to employ different wave-propagation kernels using, e.g., different discretizations, wave equation approximations, and propagation strategies. Attempts to achieve faster processing (i.e., shorter run-times) with acceptable fidelity while honoring the memory, bus bandwidth, and other system limitations, have led to innumerable kernel variations which are disclosed in literature. Yet the computational burdens remain undesirably high.